Cutaneous stimulation and generation of breathing in the fetus.

The generation of spontaneous regular breathing by cutaneous stimulation and by direct electrical stimulation of the sciatic nerve was examined in six previously apneic mature fetal lambs in utero. The fetuses were stable throughout the course of the experiments: PaO2 less than or equal to 27 mm Hg, PaCO2 less than 44 mm Hg, pH 7.29-7.34, blood pressure and heart rate steady and normal. It is shown that electrical stimulation of the fetal skin (66 cps, 4.0 msec, 6 V, 0.77 ma) can be as effective as direct stimulation of the sciatic nerve (66 cps, 4.0 msec, 1.5 V, 0.08 ma) when the higher voltage and current are used. Mechanical cutaneous stimulation also produced spontaneous breathing which, however, was short lived compared with that produced by electrical stimuli. The results are consonant with our concept of activation and recruitment of quiescent respiratory center neurones by somatic sensory stimulation, and they give fundamental support to the clinical observation of others that cutaneous stimulation is effective for the treatment of apnea of prematurity. Speculation Somatic sensory stimuli from the skin may be important determinants of the onset of breathing in the fetus and newborn.